Process for purifying naphthenic acids



Patented May 25, 1937 UNITED STTES PATET OFFICE PROCESS FOR PURIFYINGNAPHTHENIC ACIDS No Drawing. Application October 29, 1935, Serial No.47,273

6 Claims. (01. 260-108) The present invention relates to naphthenicacids, and more particularly to a new process for treating these acidswith some of the well known inorganic acids.

Naphthenic acids, such as might be obtained from the alkali wastesarising during the refining of petroleum or shale oil fractions,constitute a complex mixture of acidic compounds containing primarilycarbon, hydrogen and oxygen. They range from comparatively low boilingliquids to materials which are semi-solid and even solid at ordinarytemperatures. Their viscosities as well as the boiling points of thesesubstances are directly proportional to the viscosities and boilingpoints of the hydrocarbon fractions in which they were originallypresent.

The crude naphthenic acids which are derived by acidifying alkali Wastesformed during the treatment of various hydrocarbon fractions containvarying amounts of carbonaceous materials. One of the essential steps inthe refining of crude naphthenic acids comprises the removal of phenolicmaterials. This is carried out by a careful acidification anddistillation of the substance as described in greater detail furtherbelow. This procedure however increases the quantity of the carbonaceousmaterials present in the crude napthenic acids, and the thusdephenolized naphthenic acids have been found to contain as much as 3 to5% and even more of these carbonaceous materials. The major portion ofthe carbonaceous material exists in a finely suspended or colloidalstate and cannot be removed either by settling or centrifuging. Thenaphthenic acids containing such materials have a dark and turbid color,thereby rendering them practically useless as a commercial product.

The term alkali wastes occurring in the present specifications is meantto include the products obtained by treating with a caustic solution anextract resulting from a treatment of hydrocarbon fractions with liquidsulfur dioxide, as well as any other alkaline products or wastes arisingfrom the refining of petroleum fractions.

To produce a commercial product, it has been customary to distil thenaphthenic acids to remove the admixed carbonaceous material, and thento treat the overhead product to remove therefrom the dark color andfoul odor. However, this distillation was usually accompanied by aplugging of the still due to the presence of the undesirable materials,and the overhead product obtained during such distillation was notmaterially improved in color.

It is therefore the main object of the present invention to provide asimple and thoroughly satisfactory process for the removal from crude orsemi-refined naphthenic acids of the carbonaceous materials admixedtherein. It is a 5 further object of the present invention to provide aprocess of treating crude or semi-refined naphthenic acids to removetherefrom the dark color and foul odor.

It was previously known that the carbonaceous 10 materials andcolor-producing bodies may be removed from the crude naphthenic acidswithout any distillation by treating the naphthenic acids, either in thecrude or dephenolized state, with inorganic acids. However, it has beenfound that 15 it was necessary to use diluted concentrations of suchacids since the stronger concentrations did not produce any removal ofthe carbonaceous materials and/or color producing bodies. It wastherefore previously necessary to use the inor- 20 ganic acids, such assulfuric acid, having a concentration strength of between 50 and sincethe use of acids substantially in excess of 85% tends to cause the acidto become miscible with the naphthenic acids, so that while some slight25 separation does occur during treatment with such concentrations ofinorganic acids, the treating loss becomes so great that the process isuneconomical. The treatment of crude or semi-refined naphthenic acidswith acids having a compara- 30 tively low concentration is uneconomicalin that quite large quantities of this treating product are necessary toeffect the deposition of the carbonaceous materials and color bodies inthe form of a sludge. This process of using acids of weak 5concentration also necessitated the use of diluents, such as a lowboiling hydrocarbon solvent, these diluents aiding in a more rapid andefficient purification of the naphthenic acids.

It has now been discovered that the crude or 40 dephenolized acids(which latter are herein designated as semi-refined acids) may bepurified by treating them with sulfuric acid having a strength orconcentration above of H2804. It has been further discovered that suchtreatment 45 necessitates the use of a comparatively small percentage ofthe fuming sulfuric acid. Thus, while amounts of this reagent in theneighborhood of 10 to 15% do not give any appreciable sludge separationor color improvement, apparently due 50 to the solvent eifect of thenaphthenic acids on excess reagent, the treatment of the crude orsemi-refined naphthenic acids with amounts of the fuming sulfuric acidin the neighborhood of one-half to five percent cause the precipitation5 of a quick breaking sludge and produce a naphthenic acid which, afterfurther treatment as described hereinbelow, is of a color superior tothat of the acids refined with large amounts of low strength inorganicacid. It has been still further found that it is necessary to employ thesulfuric acid of a concentration in excess of 100% and in the amounts ofabout one-half to five percent since greater amounts of the reagent whenused for the treatment of the naphthenic acids tend to be miscible withsaid naphthenic acids or else react with them, while concentrations ofless than 100% tend to emulsify the naphthenic acid. In other words, thequantity of sulfuric acid having a concentration of over 100% to be usedin treating crude or semi-refined naphthenic acid must be such that theinorganic acid does not remain in solution in the naphthenic acid butreacts only with the carbonaceous and other foreign bodies in saidnaphthenic acid to form an immiscible sludge. Such a reaction causes theprecipitation of these undesirable materials in the form of a sludge,leaving naphthenic acid which, after a treatment with an adsorbentmaterial, has no foul odor and a very good color.

Therefore, the present invention may be said to reside in the process ofpurifying impure naphthenic acids which comprises treating them withrelatively small percentages of sulfuric acid having a concentration inexcess of 100%, said treatment tending to remove the suspendedcarbonaceous materials present in the naphthenic acids and to improvethe color thereof as well as to render them more susceptible to colorimprovement upon subsequent treatment.

The invention further resides in a process for purifying crude orsemi-refined naphthenic acids which comprises commingling said impurenaphthenic acids with quantities of fuming sulfuric acid (i. e. acidhaving a concentration in excess of 100%) insufficient to result inmiscibility of acids and sludge but only suflicient to react with thesuspended carbonaceous materials and other foreign bodies in saidnaphthenic acids, whereby said carbonaceous and foreign materials arecaused to precipitate from the acids being purified in the form of asludge, and whereby the thus purified naphthenic acids, after asubsequent treatment with an adsorbent material, such as clay or fullersearth, have good color and odor.

The invention may further be statedto reside in a process for purifyingcrude or semi-refined naphthenic acids which comprises treating themwith substantially one-half to five percent of fuming sulfuric acid.

It is, of course, obvious that the treatment of the impure naphthenicacids with the above small quantities of highly concentrated sulfuricacid must be carried out within certain definite temperature limits. Ithas been still further discovered that the best results may be obtainedif the treatment is carried out within the temperature range of 100 to175 F. and that the best results have been obtained at a temperature of135 F.

Therefore, the invention still further resides in a process for treatingimpure naphthenic acids which comprises treating them at a temperatureof between 100 and 175 F. with quantities of sulfuric acid, having aconcentration in excess of 100%, only sufficient to cause theprecipitation of the impurities in the naphthenic acid, and notsufficient to cause miscibility between the two acids and the sludge.

It has been still further discovered that a treatment of impurenaphthenic acids with fuming sulfuric acid according to the presentprocess does not require any subsequent vacuum distillation to improvecolor and odor of the acids being treated. Instead of this distillationstep, the desired result is obtainable by following the acid treatmentwith a treatment using an adsorbent material, such as clay, or by somesimilar simple filtration step.

In carrying out the process of extracting and refining naphthenic acids,an alkali waste, such as might be obtained by treating crude kerosene ora liquid sulfur dioxide extract thereof with sodium hydroxide, isacidifiedso that it is slightly acidic toward phenolphthalein. Such aprocedure prevents the liberation of the naphthenic acids from thealkaline metal salts, the naphthenates remaining as sodium naphthenates.The resulting mixture of these sodium naphthenates, phenols and admixedhydrocarbons is then steam distilled. If desired, distillation may becarried. out in the presence of small quantities of Edeleanu extract orof similar liquid hydrocarbons. The added substance may be the same asthe one from which the phenols and naphthenates were obtained by theabove described acidification. The function of the added extract, or ofits equivalent, is to prevent frothing during distillation of themixture of sodium naphthenates, phenols and hydrocarbon oils. Thedistillation, which as stated above, is preferably carried out in thepresence of steam, permits the removal of the hydrocarbon oils andphenols, the sodium naphthenates remaining in the still. The sodiumnaphthenates thus remaining as a residue are then dissolved in water andtreated with sulfuric acid to produce naphthenic acids which containonly very small amounts of phenols and admixed hydrocarbons. Thenaphthenic acids thus produced are of a poor color, contain considerableamounts of insoluble carbonaceous material and possess a foul odor. Themajor portion of this carbonaceous material and colorproducing bodies(which are present in these naphthenic acids in amounts varying from 2to 5% or higher) exists in a finely suspended or colloidal state so thatit is not removable by settling or centrifuging. The presence of thesematerials constitutes a serious objection in the marketing or furtherrefining of the thus semirefined or dephenolized naphthenic acids, andit is the refining of these semi-refined naphthenic acids whichconstitutes one of the objects of the present invention.

In carrying out the refining of the thus obtained semi-refinednaphthenic acidsaccording to the present process, a charge of naphthenicacids to be purified is commingled and agitated at a temperature ofabout 100 to 175F. with a small quantity of sulfuric acid havingconcentration above 100%. This quantity of the fumingsulfuric acidreagent must be such that the inorganic acid does not result in completemiscibility of acids and sludge but is only sufficient to cause thecoagulation of the undesirable carbonaceous and color-producing bodiesand the precipitation of the thus produced sludge from the solution.Although the quantity of the reagent necessary depends to a great extenton the amount of the undesirable constituents in the impure naphthenicacids, it has been found that ordinarily one-half to five percent byvolume is sufiicient to produce the desired result, and that goodresults have been obtained with the use of about four percent of fumingsulfuric acid.

After the removal of the sludge from the supernatant naphthenic acidsthe latter may be water-washed and clay treated. The resultingnaphthenic acids have a higher organic acidity as compared with the acidnumber of the original semi-refined acids. Also, the thus refinednaphthenic acids have a six to seven N. P. A. color, being transparentwhen viewed through a four ounce oil sample bottle, whereas the sameacids before refining were black and had no such transparency. The thusrefined naphthenic acids also possess a much larger degree of fluiditythan the crude product, are free from admixed carbonaceous materials,and have a sweet odor.

The same semi-refined naphthenic acids, when treated with approximatelythe same quantities of fuming sulfuric acid at temperatures below 100 F.and above 175 F. did not produce satisfactory results in that thecarbonaceous materials did not precipitate in the form of a sludge.

As a modification of the above described method of operation, in whichspecial precautions were first taken to remove the phenols from thecrude naphthenic acids, the fuming sulfuric acid treatment may beemployed in purifying crude naphthenic acids, i. e. those from which thephenols have not been removed. In such a case, the naphthenate soapscontaining the phenols are first treated with sulfuric acid of anystrength for the purpose of liberating the naphthenic acids. The waterproduced during this treatment is then removed, and the resultantmixture of naphthenic acids and phenols is then treated, according tothe present invention with small quantities of fuming sulfuric acid onlysuffioient to cause the carbonaceous materials in said mixture toprecipitate in the form of a sludge. Obviously, the above method ofoperation is applicable in cases where the presence of phenolicmaterials together with the naphthenic acids is not undesirable.

Although the term fuming sulfuric acid, as

used in the petroleum industry, means a sulfuric acid of a concentrationof about 103%, within the meaning of the present disclosure it includessulfuric acids of a concentration above 100%.

This invention is not limited to any specific example herein set forth,nor to naphthenic acids derived from any particular hydrocarbon fractionas all naphthenic acids derived from any source, may be refined thereby.As to the scope of this invention, reference is made to the appendedclaims.

I claim:

1. In a process for purifying naphthenic acids contaminated withcarbonaceous materials, the step of contacting said acids at atemperature substantially between F and F. with a quantity of sulfuricacid having a concentration above 100%, said quantity of sulfuric acidbeing only suificient to cause precipitation of said carbonaceousmaterials.

2. A process according to claim 1, wherein the acid treatment isfollowed by a treatment with an adsorbent material.

3. In a process for purifying naphthenic acids contaminated withcarbonaceous materials, the step of contacting said acids at atemperature substantially between 100 F. and 175 F. with quantities offuming sulfuric acid only sufficient to cause precipitation of saidcarbonaceous materials, but insufl'icient to cause miscibility betweenthe acid and the precipitated carbonaceous materials.

4. A process according to claim 3, wherein the quantity of fumingsulfuric acid is substantially between one-half of one percent and fivepercent by volume of the naphthenic acid being treated.

5. A process for deodorizing and decolorizing impure naphthenic acidswhich comprises treating said acids at a temperature substantiallybetween about 100 F. and 175 F. with fuming sulfuric acid in a quantitysufiicient to cause the precipitation of the impurities in the form of asludge, but insufficient to cause miscibility between the acids and thethus formed sludge, and subsequently treating the naphthenic acids withan adsorbent material.

6. In a process for purifying naphthenic acids contaminated withcarbonaceous materials the steps of contacting said acids with aquantity of sulfuric acid having a concentration above 100% onlysufiicient to cause precipitation of said carbonaceous materials butinsufiicient to cause miscibility between the acid and the precipitatedcarbonaceous materials, and operating within such temperature range thatsaid precipitation of carbonaceous materials is effected.

DONALD E. CARR.

